1. Field of the Invention
The present invention relates to a metal magnetic thin film type magnetic recording medium onto/from which recording and/or reproduction is carried out by sliding of a magnetic head and in particular, to an improvement of a carbon protection film.
2. Description of the Prior Art
Conventionally, the magnetic recording medium widely used is a so-called paint-type magnetic recording medium which is prepared by coating a non-magnetic support body with a magnetic paint made from a powder magnetic material such as an oxide magnetic powder or an alloy magnetic powder dispersed in an organic binder such as vinyl chloride--vinyl acetate copolymer, polyester resin, urethane resin, and the like.
In contrast to this, with increasing requirement for a high-density recording, attention is paid on a so-called metal magnetic thin film type recording medium which is prepared by directly applying a metal magnetic material such as a Co-Ni alloy, Co-Cr alloy, Co-O alloy by way of plating or vacuum thin film formation means (vacuum deposition, sputtering, ion plating method, and the like).
This metal magnetic thin film type magnetic recording medium has various merits such as an excellent anti-magnetization force and rectangular ratio and enables to obtain an extremely thin magnetic layer, which in turn suppresses the recording magnetization loss and the thickness loss during reproduction, enabling to obtain an excellent electromagnetic conversion characteristic in a short wavelength. Moreover, because there is not need of mixing a non-magnetic material such as a binder in the magnetic layer, it is possible to increase the magnetic material filling density. Consequently, it is considered that the metal magnetic thin film type magnetic recording medium will become a main stream of the high-density magnetic recording because of its excellent magnetic characteristic.
Furthermore, in order to improve the electro-magnetic conversion characteristic of this type of magnetic recording medium so as to obtain a high output in a shorter wavelength, a so-called oblique-deposited medium has been suggested and used in practice. This oblique-deposited medium is a magnetic metal thin film type magnetic recording medium having a magnetic layer formed by way of so-called oblique deposition, i.e., a magnetic metal is deposited in an oblique direction onto a traveling non-magnetic support body.
On the other hand, in order to answer to a further higher density recording, there is a tendency that the magnetic recording medium is made flat so as to reduce a spacing loss. The flattening of the magnetic recording medium is accompanied by increase of the friction between a head and a medium, increasing the shearing stress generated in the medium. Here, in order to improve the sliding durability, there has been studied a technique to form a protection film on the surface of the magnetic layer.
As such a protection film, a carbon film, quartz (SiO.sub.2) film, a zirconia (ZrO.sub.2) film, and the like have been studied and implemented in practice for a hard disc. As for the carbon protection film, a diamond-lie carbon (hereinafter, referred to as DLC) film is studied as a harder film. The DLC film is formed by using a sputtering method, a chemical vapor phase epitaxy (hereinafter, referred to as CVD) method, and the like.
In the sputtering method, firstly, an electric field and a magnetic field are used for plasmatizing an inert gas such as argon gas and the plasmatized argon ion is accelerated so that its kinetic energy strikes out a target atom. The struck out atom is accumulated on a opposing substrate, thus forming a film as a purpose. This sputtering method has a poor productivity from an industrial viewpoint because the aforementioned DLC film is formed with a low speed.
On the contrary, the CVD method is a chemical process in which the plasma energy generated by an electric field and a magnetic field causes a chemical reaction of a material gas such as decomposition and synthesis. The DLC film formation speed is faster than in the sputtering method.
Thus, by providing the carbon protection film by way of the aforementioned methods, the magnetic recording medium significantly increases its sliding durability.
However, these years, the magnetic recording apparatus tends to become smaller and to have a greater capacity. Especially for the data storage use which requires a high reliability, a further improved sliding durability is required.
Moreover, the magnetic head of the magnetic recording/reproduction apparatus has a lower floating amount. As the extreme case of the floating amount, a so-called contact method is also suggested in which recording and reproduction are carried out with the magnetic head always in contact with the surface of a magnetic recording medium.
In the magnetic recording medium in which recording and/or reproduction is carried out by way of contact sliding between a magnetic head and a magnetic recording medium surface, it is necessary to further reduce the friction and improve the sliding durability.